The improvements in mirror manufacturing techniques during the 16th century caused an increasing use of optical mirror elements in interior architecture. For example, the overlay of a portion of a wall with a reflective surface generated the impression of space enhancement and an increase of depth perception. Since then, mirrors became essential components capable of improving the comfort of an ambience through a widening in the perceived volume. In general, in modern and contemporary architecture, reflective surfaces are used to provide for specific perceptions by an observer.
The following disclosure is at least partly based on specific nanoparticle based reflective units, and their application in the fields of active and passive illumination such as in lighting in general or outdoor facade applications.
As will be disclosed herein, the specific nanoparticle based reflective units may be used to provide for a specific visual perception of an outdoor or indoor wall for the observer. Those units may provide specific chromatic and reflective features that provide for properties of sun imitating lighting systems such as described, for example, in the international patent application PCT/EP2014/059802, filed on 13 May 2014 by the same applicants, in which reflective and diffusing layers are combined.
For example, in modern architecture, facade structures combine a large variety of functions. Primarily, there is the aesthetic aspect addressing the perception of a building and how it is perceived in the environment of other buildings, under different weather conditions, and respective illumination situations. Furthermore, active illumination of buildings allows providing specific visual impressions of buildings even at night.
On Rayleigh-like diffusing layers, several applications such as EP 2 30 478 A1, EP 2 304 480 A1, and WO 2014/076656 A1, filed by the same applicants, disclose lighting systems that use a light source producing visible light, and a panel containing nanoparticles used in transmission, i.e. the light source and the illuminated area are positioned on opposing sides of the panel. During operation of those lighting systems, the panel receives the light from the light source and acts in transmission as a so-called Rayleigh diffuser, namely it diffuses incident light similarly to the earth atmosphere in clear-sky conditions. Specifically, the concepts refer to directional light with lower correlated color temperature (CCT), which corresponds to sunlight, and diffuse light with larger CCT, which corresponds to the light of the blue sky.
Introducing a reflective feature as, for example, in PCT/EP2014/059802 mentioned above, however, may affect the perception due to the presence of the reflection. In particular, for lighting systems that intend to trick the eye by providing a natural imitating sky sun illumination, for example together with a visual appearance of the sky and the sun, inhomogeneities in color and luminance are avoided or at least reduced in order to preserve the desired optical and visual effect. On the other side, a mirror-like facade may—similar to large windows—disadvantageously not be recognized by birds flying against and impacting on the facade that is, for example, perceived as the sky.
Thus, the present disclosure is directed, at least in part, to improving or overcoming one or more aspects of prior systems.